Haskell Dockerfile Linter
A smarter Dockerfile linter that helps you build best practice Docker
images. The linter is parsing the Dockerfile into an AST and performs rules on
top of the AST. It is standing on the shoulders of ShellCheck to lint
the Bash code inside RUN instructions.
:globe_with_meridians: Check the online version on
hadolint.github.io/hadolint
How to use
You can run hadolint locally to lint your Dockerfile.
hadolint <Dockerfile>
hadolint --ignore DL3003 --ignore DL3006 <Dockerfile> # exclude specific rules
hadolint --trusted-registry my-company.com:500 <Dockerfile> # Warn when using untrusted FROM images
Docker comes to the rescue to provide an easy way how to run hadolint on most
platforms.
Just pipe your Dockerfile to docker run:
docker run --rm -i hadolint/hadolint < Dockerfile
Install
You can download prebuilt binaries for OSX, Windows and Linux from the latest
release page. However, if it doesn't work for you, please fall back to
Docker, brew or source installation.
If you are on OSX you can use brew to install hadolint.
brew install hadolint
On Windows you can use scoop to install hadolint.
scoop install hadolint
As shown before, hadolint is available as a Docker container:
docker pull hadolint/hadolint
If you need a Docker container with shell access, use the Debian or Alpine
variants of the Docker image:
docker pull hadolint/hadolint:latest-debian
docker pull hadolint/hadolint:latest-alpine
You can also build hadolint locally. You need Haskell and the stack
build tool to build the binary.
git clone https://github.com/hadolint/hadolint
cd hadolint
stack install
hadolint supports specifying the ignored rules using a configuration file. The configuration
file should be in yaml format. This is one valid configuration file as an example:
ignored:
- DL3000
- SC1010
Additionally, hadolint can warn you when images from untrusted repositories are being
used in Dockerfiles, you can append the trustedRegistries keys to the configuration
file as shown below:
ignored:
- DL3000
- SC1010
trustedRegistries:
- docker.io
- my-company.com:5000
Configuration files can be used globally or per project. By default, hadolint will look for
a configuration file in the current directory with the name .hadolint.yaml
The global configuration file should be placed in the folder specified by XDG_CONFIG_HOME,
with the name hadolint.yaml. In summary, the following locations are valid for the configuration
file, in order or preference:
$PWD/.hadolint.yaml$XDG_CONFIG_HOME/hadolint.yaml~/.config/hadolint.yaml
In windows, the %LOCALAPPDATA% environment variable is used instead of XDG_CONFIG_HOME
Additionally, you can pass a custom configuration file in the command line with
the --config option
hadolint --config /path/to/config.yaml Dockerfile
Inline ignores
It is also possible to ignore rules by using a special comment directly above the Dockerfile
instruction you want to make an exception for. Ignore rule comments look like
# hadolint ignore=DL3001,SC1081. For example:
# hadolint ignore=DL3006
FROM ubuntu
# hadolint ignore=DL3003,SC1035
RUN cd /tmp && echo "hello!"
Inline ignores will only work if place directly above the instruction.
Integrations
To get most of hadolint it is useful to integrate it as a check to your CI
or to your editor to lint your Dockerfile as you write it. See our
Integration docs.
Rules
An incomplete list of implemented rules. Click on the error code to get more
detailed information.
-
Rules with the prefix DL originate from hadolint. Take a look at
Rules.hs to find the implementation of the rules.
-
Rules with the SC prefix originate from ShellCheck (Only the most
common rules are listed, there are dozens more)
Please create an issue if you have an idea for a good rule., Rule, Description, :-------------------------------------------------------------, :----------------------------------------------------------------------------------------------------------------------------------------------------, DL3000, Use absolute WORKDIR., DL3001, For some bash commands it makes no sense running them in a Docker container like ssh, vim, shutdown, service, ps, free, top, kill, mount, ifconfig., DL3002, Last user should not be root., DL3003, Use WORKDIR to switch to a directory., DL3004, Do not use sudo as it leads to unpredictable behavior. Use a tool like gosu to enforce root., DL3005, Do not use apt-get upgrade or dist-upgrade., DL3006, Always tag the version of an image explicitly., DL3007, Using latest is prone to errors if the image will ever update. Pin the version explicitly to a release tag., DL3008, Pin versions in apt-get install., DL3009, Delete the apt-get lists after installing something., DL3010, Use ADD for extracting archives into an image., DL3011, Valid UNIX ports range from 0 to 65535., DL3012, Provide an email address or URL as maintainer., DL3013, Pin versions in pip., DL3014, Use the -y switch., DL3015, Avoid additional packages by specifying --no-install-recommends., DL3016, Pin versions in npm., DL3017, Do not use apk upgrade., DL3018, Pin versions in apk add. Instead of apk add <package> use apk add <package>=<version>., DL3019, Use the --no-cache switch to avoid the need to use --update and remove /var/cache/apk/* when done installing packages., DL3020, Use COPY instead of ADD for files and folders., DL3021, COPY with more than 2 arguments requires the last argument to end with /, DL3022, COPY --from should reference a previously defined FROM alias, DL3023, COPY --from cannot reference its own FROM alias, DL3024, FROM aliases (stage names) must be unique, DL3025, Use arguments JSON notation for CMD and ENTRYPOINT arguments, DL3026, Use only an allowed registry in the FROM image, DL3027, Do not use apt as it is meant to be a end-user tool, use apt-get or apt-cache instead, DL3028, Pin versions in gem install. Instead of gem install <gem> use gem install <gem>:<version>, DL4000, MAINTAINER is deprecated., DL4001, Either use Wget or Curl but not both., DL4003, Multiple CMD instructions found., DL4004, Multiple ENTRYPOINT instructions found., DL4005, Use SHELL to change the default shell., DL4006, Set the SHELL option -o pipefail before RUN with a pipe in it, SC1000, $ is not used specially and should therefore be escaped., SC1001, This \c will be a regular 'c' in this context., SC1007, Remove space after = if trying to assign a value (or for empty string, use var='' ...)., SC1010, Use semicolon or linefeed before done (or quote to make it literal)., SC1018, This is a unicode non-breaking space. Delete it and retype as space., SC1035, You need a space here, SC1045, It's not foo &; bar, just foo & bar., SC1065, Trying to declare parameters? Don't. Use () and refer to params as $1, $2 etc., SC1066, Don't use $ on the left side of assignments., SC1068, Don't put spaces around the = in assignments., SC1077, For command expansion, the tick should slant left (` vs ´)., SC1078, Did you forget to close this double-quoted string?, SC1079, This is actually an end quote, but due to next char, it looks suspect., SC1081, Scripts are case sensitive. Use if, not If., SC1083, This {/} is literal. Check expression (missing ;/\n?) or quote it., SC1086, Don't use $ on the iterator name in for loops., SC1087, Braces are required when expanding arrays, as in ${array[idx]}., SC1095, You need a space or linefeed between the function name and body., SC1097, Unexpected ==. For assignment, use =. For comparison, use [/[[., SC1098, Quote/escape special characters when using eval, e.g. eval "a=(b)"., SC1099, You need a space before the #., SC2002, Useless cat. Consider cmd < file | .. or cmd file | .. instead., SC2015, Note that A && B || C is not if-then-else. C may run when A is true., SC2026, This word is outside of quotes. Did you intend to 'nest '"'single quotes'"' instead'?, SC2028, echo won't expand escape sequences. Consider printf., SC2035, Use ./*glob* or -- *glob* so names with dashes won't become options., SC2039, In POSIX sh, something is undefined., SC2046, Quote this to prevent word splitting, SC2086, Double quote to prevent globbing and word splitting., SC2140, Word is in the form "A"B"C" (B indicated). Did you mean "ABC" or "A\"B\"C"?, SC2154, var is referenced but not assigned., SC2155, Declare and assign separately to avoid masking return values., SC2164, Use cd ... || exit in case cd fails., ## Develop
If you are an experienced Haskeller we would be really thankful if you would
tear our code apart in a review.
Setup
-
Clone repository
git clone --recursive git@github.com:hadolint/hadolint.git
-
Install the dependencies
stack install
REPL
The easiest way to try out the parser is using the REPL.
# start the repl
stack repl
# parse instruction and look at AST representation
parseString "FROM debian:jessie"
Tests
Run unit tests.
stack test
Run integration tests.
./integration_test.sh
AST
Dockerfile syntax is fully described in the Dockerfile reference. Just take
a look at Syntax.hs in the language-docker project to see the AST definition.
Alternatives
